http://www.bandepleteduranium.org/en/a/32.html
1. Ore
Uranium mineral can be found everywhere on earth, but only mineral of economic interest is called ore. Often extraction is too costly, for uranium can occur in very complex combinations with other elements. Usually the quantity of uranium in rocks is too low to make extraction worthwhile.
Even the uranium ore usually mined contains a very small percentage of uranium (0.12 %). Since 1999, Canadian ore deposits have been explored containing as much as 13% uranium. Ores called pitchblende, uraninite and carnotite are mostly mined.
All ore contains radioactive uranium, lead, polonium, bismuth, thorium, radium, protactinium and radon gas. These are radioactive decay products from uranium. Also other toxic elements like nickel, cadmium, molybdenum, vanadium, arsenic and mercury may be present in the minerals. Radon gas is a particular danger. The radioactive gas easily escapes from the rock and always surrounds a rock or mine site.
2. Mining technologies
Different techniques are used to obtain uranium from the rock. Uranium is extracted from ore at uranium mills and at in situ leach (ISL) facilities. Uranium is also obtained as by-product from non-conventional uranium plants, like the phosphate industry. Mining and milling generate waste rock, sludge, tailings (dried sludge), wastewater and leached areas.
Currently, over half of the world's uranium comes from underground mines, about 27% from open pits and 19% from ISL. In the US, about 16% of the domestically produced uranium comes from the phosphate industry.
2.1.1. Conventional uranium mines
Mining process
Traditionally, uranium ore was dug from open pits. In open pit mines, the ore deposits are located near the surface. To excavate the rocks, the traditional mining methods of drilling and blasting are used. These pits often have enormous dimensions.
In the 1970?s shaft mines opened to employ deep underground ore bodies. Underground mining involves construction of access tunnels and shafts.
Because ore contains such low concentrations of uranium, huge amounts of rock must be mined.
To keep groundwater out of the mine during operations, large amounts of contaminated water are pumped out and mostly released into rivers and lakes. When the pumps are shut down after the closure of the mine, there is a great risk of groundwater contamination from the rising water level in the shafts.
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